Jesus, people really should address their emotional issues to a therapist, not in video games. You can add any sexual content in a game - threesomes, orgies, incest, bestiality, watersports, gay, rape, loli - and people not liking said content will usually just quietly skip it, or ignore it. Add Nice Time for Roo, and a small but VERY vocal minority comes out of the woodshed.
To be fair, Nice Time for Roo is quite a different beast to all the others on that list. At the end of the day, it's a matter of tone.
Simple debaucheries like threesomes and orgies are already perfectly wholesome unless you're bloody Victorian, as participating parties all go in consensually with the intention and expectation to simply have a good time. They fit right into a sexually open cultural setting.
Those that don't fit are simply...not present in full.
Watersports isn't presented at all, and it's one of the lighter fetishes. Unless you want to count squirting, but scientifically it's still undecided.
As I recall, there isn't any - for lack of a better word - "proper" rape in this game. Not the type where the victim would have to live with emotional and sometimes physical scars for life, or the type that are near-death experiences. It's less rape and more regular consensual sex with a unique, overly vigorous, DnD themed take on foreplay.
Bestiality isn't really bestiality when the beast in question is talking to you about his home town mid-coitus.
And uh...well the whole "she's actually older than the atoms in my body" doesn't work in court, but it helps those people sleep at night after their wank so long as no SWAT teams bust in. There aren't any of that in this game regardless of excuse.
Point is, these fetishes can be sanitized in one way or another to not be emotionally upsetting...to various degrees of effectiveness (seriously it won't work in front of a jury). Not all kinks are created equal, and I'm sure there are kinks you'd consider more than reasonable for people to be outraged about. CoC2's kink writing has always been in this sanitized realm, where all of it is at least somewhat consensual, and more importantly, fully enjoyable for everyone involved. None of it is genuinely disturbing, enraging or depressing. That is the tone of this game.
In the case of Nice Time for Roo, the emotional upset IS what makes it work. It has to be enraging and humiliating, and not even humiliating in the kinky way. Sanitize Nice Time for Roo and it's no longer Nice Time for Roo, at least not Nice Time for Roo enough for the people who are into that stuff. Consensual, fully enjoyable Nice Time for Roo is just pimping with a heavy discount, which we already have in the form of deploying Cait like a pokemon.
If CoC2 was the kind of dark game that presented all of those fetishes in their fully fucked up and in at least one case severely illegal glory, then yeah, people would let Nice Time for Roo slide. But it isn't. People in this section of the kink pool don't want to go any deeper, so it won't do to start digging potholes beneath their tippy-toed feet.
As a last note: being on this end of the internet for too long can really skew your views. Ask 100 people on the street who is more likely to need a therapist: the person into Nice Time for Roo or the person repulsed by it, 98 is gonna say the former. Some of us are being good little stoics about it and that's cool, but let's not pretend it's even remotely unreasonable to be upset about something that ruins decades long marriages. The vocal minority in this case comes from a majority that's too desensitized to actually bother speaking up, and that woodshed they came from is fucking enormous, filled with enough people to declare itself a major city.